Uni- and bidirectional wide angle CT colonography: effect on missed areas, surface visualization, viewing time and polyp conspicuity.
East JE., Saunders BP., Boone D., Burling D., Halligan S., Taylor SA.
The effect of field of view on mucosal visualisation and reader efficiency during three-dimensional endoluminal CT colonography (CTC) was investigated. Twenty CTC datasets were reviewed at standard 90-degree and "wide" 140-degree viewing angles using customised viewing software (V3D colon; Viatronix), which listed number and size of missed mucosal areas ("missed regions tool") and percentage mucosal visualisation. We compared: (1) unidirectional and bidirectional flythrough using 140- versus 90-degree viewing angles; (2) reader analysis time comparing unidirectional 140-degree flythrough versus bidirectional 90-degree flythrough; (3) paired image snapshots of 12 polyps taken at each field of view were reviewed to assess conspicuity. All patients underwent conventional colonoscopy. Bidirectional 140-degree review reduced the numbers of missed areas by between eight- and 40-fold depending on size category, including those >1,000 mm(2), compared with standard 90-degree bidirectional flythrough (P < 0.001). Combined prone-supine unidirectional 140-degree flythrough and missed area review was 3.8 min faster than 90-degree bidirectional review (9.3 versus 5.5 min, P < 0.0001) for the same surface visualisation. When viewed as pairs, polyps were rated more conspicuous with a 90-degree field of view, P = 0.03. Wide-angle (140-degree) CTC can reduce both numbers of missed areas and review times. However, this may be at the expense of polyp conspicuity.